The os and the apps that are built in are quite nice basically just look and feel like stock android. Beyond the built in stuff it is a bit more hit and miss if you want to stick to FOSS only like osmand is ok for maps but not really close to google maps. Personally I stick to only FOSS apps but you dont need to be as paranoid as me even while using graphene you can install apps from the play store including google apps. Graphene does have additional privacy protections when using google apps and you can take that a step further by having a separate profile for apps you dont trust. Really though you should read through some of the docs on the graphene website because only you can decide whether the convenience tradeoffs are worth it for your specific case.